The literature on previous attempts at isotope separation is quite extensive. The present methods in production center on the extremely costly and inefficient diffusion process. This process is only viable in very large scale installations.
Recently, a number of proposals for using lasers to separate isotopes have appeared. They include frequency selective excitation of one isotope-shifted transition. The excited species can then be swept out of the interaction region by chemical or ionization processes. These techniques require narrow-banded lasers, stabilized to distinguish in frequency between very closely spaced levels. These requirements often prevent very high powered or efficient systems required for production applications.
Another suggested method using lasers involves deflection of one isotope vs. another in an atomic or molecular beam using the momentum transfer from resonantly absorbed laser light. Again, these techniques require a very narrow-banded laser, good stability, and, in addition, an atomic beam apparatus which generally means a lower density of atoms than, say, a gas cell.
It is an object of the invention herein described to provide apparatus and method for selective excitation of one particular isotope into a state where it can readily be swept out and collected, in particular by ionization. It is a process employing pulsed lasers where the primary requirement is to have reasonably short pulses -- microsecond or nanosecond regime depending upon the atomic or molecular species involved same delay between pulses, and the same handedness of circular polarization. A comparatively gross timing and stability is all that is required of the lasers, far less stringent constrictions than for other laser techniques.
Typically, transition linewidths are tens to hundreds of MHz wide. (3 .times. 10.sup.4 MHz = 1cm.sup.-.sup.1 in Energy) Isotope shifts of spectral lines are typically hundreds to about a thousand MHz. Thus the other techniques require lasers narrower than these isotope shifts and stabilized to wander at most one linewidth. In the present technique, typical laser linewidths and jitters of tens of thousands of MHz (and sometimes more) are allowable. This permits more powerful laser systems to be used. The laser technology exists and is well-developed. The method is quite efficient and especially adaptable to large scale production because of its simplicity. It must be emphasized again that this process can be applied to either atomic or molecular species -- whichever is more efficient for the isotope to be separated.
Other objects, features and advantages of the invention will be apparent from the following detailed description of a preferred embodiments thereof taken in conjunction with the accompanying drawings in which: